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net/packet: call packet_parse_headers after virtio_net_hdr_to_skb

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SOCK_RAW packet sockets incorrectly drop VLAN-tagged GSO packets
without VIRTIO_NET_HDR_F_NEEDS_CSUM.

packet_parse_headers() sets skb->protocol to VLAN but advances
skb->network_header past the VLAN tags. virtio_net_hdr_to_skb()
then flow dissects these packets, which parses the network header as a
VLAN tag, and fails.

Call packet_parse_headers() after virtio_net_hdr_to_skb() instead.

This matches tun_get_user() and tap_get_user() and thus simplifies
overall complexity.

Commit 01fdecc048 ("net: packet: fix wrong transport_header when
sending VLAN-tagged frame") fixed the same issue for the transport
header probe in packet_parse_headers(). That probe is now skipped if
virtio_net_hdr_to_skb() already set the transport header, avoiding a
redundant dissection.

Implementation details:
- Do not set skb->protocol to the RX wildcard ETH_P_ALL. SOCK_RAW then
  derives it from the link layer header, as before. SOCK_DGRAM now
  leaves it 0, or derives it from gso_type for GSO with NEEDS_CSUM.
- Keep virtio_net_hdr_set_proto() last, so that the link layer protocol
  takes priority over gso_type.

Reported-by: Junnan Zhang <zhangjn_dev@163.com>
Closes: https://lore.kernel.org/netdev/20260821085722.24036-1-zhangjn_dev@163.com/
Fixes: dfed913e8b ("net/af_packet: add VLAN support for AF_PACKET SOCK_RAW GSO")
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Link: https://patch.msgid.link/20261007175816.3138556-1-willemdebruijn.kernel@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Willem de Bruijn 2026-10-07 13:57:30 -04:00 • committed by Jakub Kicinski
commit 513e23857a
1 changed files with 15 additions and 10 deletions
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